In a semiconductor manufacturing process, a charged particle beam application apparatus utilizing a charged particle beam such as an electron beam is used for measuring or inspecting of a size or a shape of a semiconductor device. In addition, a general-purpose charged particle beam application apparatus is used to observe an object other than the semiconductor device. An example is a Scanning Electron Microscope (SEM). The SEM irradiates a sample to be observed with the electron beam generated from an electron source, secondary electrons generated by irradiation is detected by a detector, is converted into an electrical signal, and then an image is generated from the electrical signal.
In recent years, miniaturization of the semiconductor device has advanced and high resolution of the SEM is essential. In order to achieve high resolution, it is necessary to reduce a size of the electron beam on a sample surface. Therefore, an aberration corrector for correcting an aberration generated by causing the electron beam to pass through an electromagnetic lens is effective.
JP-T-2009-528668 (PTL 1) discloses a technique that corrects an aberration of the secondary electrons from a sample by an aberration corrector (mirror aberration corrector) using a mirror. PTL 1 discloses the following matters.
“A second magnetic deflector is disposed to receive a first energy dispersive electron diffraction pattern from an electrostatic lens. In addition, the second magnetic deflector is configured to project a second non-dispersive electron diffraction pattern on a first emission surface of the second magnetic deflector. The deflector also has an electronic mirror configured to correct one or a plurality of aberrations. The electronic mirror is disposed so as to reflect the second non-dispersive electron diffraction pattern on the second magnetic deflector to project a second energy dispersive electron diffraction pattern on a second emission surface of the second magnetic deflector.” (see abstract).
Moreover, JP-A-62-113350 (PTL 2) discloses a technique that obtains an unfiltered image having the same size as that of an energy filter image by disposing transfer lenses at vertically symmetrical positions of a spectrometer in an electron microscope which includes a plurality of spectrometers for separating an electron beam from a sample according to energy and switches between the energy filter image and the unfiltered image (see claims).